1. Field of the Invention
The present invention relates to a static-pressure gas bearing mechanism to which an anti-moment measure is applied for a rod to which a fluctuating load acts and more specifically, a static-pressure gas bearing mechanism suitable for support of the rod for straight conveyance of a work used in a vacuum environment or a clean environment.
2. Description of the Related Art
In general, a straight conveying device usable in a vacuum environment or a clean environment such as a clean room is provided with the above rod for conveyance, and a contact-supporting method such as a slide bearing, a ball bush or the like is used at a bearing portion of the rod to handle dust generation at the bearing portion as necessary. When the bearing portion is in the contact supporting type in this way, dust generation can not be prevented basically and moreover, generation of dust is increased by rise of a rod driving speed, which causes problems of lowered cleanliness, accelerated bearing abrasion and drop of device durability.
In order to avoid these problems, it is necessary to limit a shift to high speed of the driving speed, and it lowers work processing productivity.
On the other hand, support of the rod with a non-contact support type static-pressure gas bearing has been extremely widely known. If this non-contact support type static-pressure gas bearing is applied to the support of the rod in the above-mentioned conveying device, dust generation can be suppressed to the minimum and high-speed conveying of works in a vacuum environment and a clean environment becomes possible.
However, due to the weight of the rod or an external force acting on the rod, a moment acts on a support portion of the rod supported by a static-pressure gas bearing, by which a part of the rod might be brought into contact with the static-pressure gas bearing. In this case, similar problems to the above contact support type will occur.